Chiral Effective Lagrangian For Heavy-light Mesons From QCD

Quantum chromodynamics(QCD)has been well verified and widely accepted as a fundamental theory describing strong interactions.However,the coupling constant of QCD increases at low energy,which makes traditional perturbation theory invalid in low energy.To describe low-energy hadron,physicists have established an effective theory named chiral effective theory.Chiral effective Lagrangian is constructed based on the the chiral symmetry and other symmetries of strong interaction with a certain power-counting rule.Although chiral effective theory has made great success,it still should be based on fundamental QCD.There must be an internal connection between chiral effective theory and fundamental QCD,and it is of great importance to reveal this connection,both theo-retically and practically.There have been literatures starting from QCD,deducing the chiral effective La-grangian of pseudo-scalar mesons,and obtaining the low-energy constant expression de-scribed by the quark self-energy of QCD.It is found through numerical calculation that the resulting low-energy constant matches with experimental data within accuracy.Later,this method was extended to the system with scalar mesons,vector mesons and psudo-vector mesons.However,those works could only describe light mesons that contain only light quarks,mesons that contain heavy quark have not been involved.As we all know,heavy-quark symmetry is another important symmetry of QCD,it allows us to make ap-proximate treatment on some physical quantities through 1/mQexpansion.Therefore,it's significant to extend this method to the chiral effective Lagrangian of heavy-light mesons.Our main work is to derive the chiral effective Lagrangian of heavy-light mesons from QCD,and determine the low-energy constant expressed by the momentum integral of quark self-energy.Through numerical calculations,we found that the low-energy con-stants we calculated are consistent with the experimental results,but there are still certain errors.Therefore,we made 1/m_Q correction for the chiral effective Lagrangian of the heavy-light meson.As a result,we found that the mass and decay width of the heavy-light mesons we gave are in good agreement with the experiment.With the discovery of more and more multiple heavy-light meson excited states,it is urgent to study the properties of these excited states theoretically and experimentally.So we extend this method to include the chiral effective Lagrangian of the excited state of heavy-light mesons.The masses of the excited states we got are similar to the experimental result.Meanwhile,our result shows that B meson excited state B_J(5970)could be a particle of excited state(3/2)~-with a quantum number 1~-or 2~-.